Wednesday, 8 April 2015

Light skin

Light skin is a naturally occurring Human skin color which has little eumelanin pigmentation and which has been adapted to environments of low UV radiation. Light skin is most commonly found amongst people of Europe and East Asia. People with light skin pigmentation are often referred to as white or yellow, although these usages can be ambiguous in some countries where it is used to refer specifically to certain ethnic groups or populations.

It has been hypothesized that dark skin pigmentation was the original condition for the genus Homo, including Homo sapiens. However, as populations migrated away from the tropics between 125,000 and 65,000 years ago into areas of low UV radiation, they developed light skin pigmentation as an evolutionary selection acting against vitamin D depletion. Based on ancient DNA analysis conducted in 2014 on human skeletal remains from western Europe, this change from dark to light skin pigmentation likely occurred only recently for at least some Europeans. Paleogenomics researcher Carles Lalueza-Fox of the Pompeu Fabra University in Spain and his colleagues observed that a 7,000 year old hunter-gatherer from the La BraƱa-Arintero labyrinthine cave in the Cantabrian Mountains possessed the allele for blue eyes but not the European mutations for lighter skin pigmentation.

Humans with light skin pigmentation have skin with low amounts of eumelanin, and possess fewer melanosomes than humans with dark skin pigmentation. Light skin provides better absorption qualities of ultraviolet radiation. This helps the body to synthesize higher amounts of vitamin D for bodily processes such as calcium development.

Light-skinned people who live near the equator with high sunlight are at an increased risk of folate depletion. As consequence of folate depletion, they are at a higher risk of DNA damage, birth defects, and numerous types of cancers, especially skin cancer.

The distribution of indigenous light-skinned populations is highly correlated with the low ultraviolet radiation levels of the regions inhabited by them. Historically, light-skinned indigenous populations almost exclusively lived far from the equator in high latitude areas with low sunlight intensity; for example, in Canada, Mongolia, Russia, Scandinavia, and Northern, Western, Southern and Eastern Europe. Due to mass migration and increased mobility of people between geographical regions in recent centuries, light-skinned populations today are found all over the world, even in tropical climates

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